In recent years, mobile devices (such as portable telephone machines) used in mobile communication systems, such as a PDC-P (Personal Digital Cellular-Packet) system, have been able to not only have audio communication, but also exchange electronic mails and receive various contents via the Internet. When a mobile device receives an electronic mail, a mail server notifies the mobile device of the reception of the electronic mail that is addressed to the mobile device and has been delivered to the mailbox in the mail server. Upon receipt of this reception notification, the mobile device accesses the mail server to collect the mail. Here, to notify the mobile device of the reception, the mail server transmits a reception notification to the mobile communication system, and a device such as an exchange center node in the mobile communication system establishes a packet link with the mobile device to which the reception notification is directed. Through this packet link, the reception notification is transmitted to the mobile device.
Conventionally, a reception notification directed to a mobile device used in a mobile communication system has been transmitted through a packet link established between the mobile device to which the reception notification is directed and an exchange center node in the mobile communication system, as descried above. However, while a packet link has already been established between the mobile device and the exchange center node (such as a time when the user of the mobile device is reading a homepage), a new packet link is required for performing reception notification when there is a reception directed to the mobile device. In such a situation, as the number of mobile devices in the radio zone increases, the number of packet links established for reception notification also increases. As a result, the resource of packet links that should be used for information transmission and reception is allocated to reception notification, and the network resource cannot be efficiently utilized as a whole.
Also, one of the applications that are most frequently used on the Internet at present is electronic mail. There are roughly two fashions of electronic mail transmission: one is intended for electronic mails that need to be delivered to the other party instantly; and the other is intended for electronic mails such as advertisements that do not need to be delivered to the other party instantly. The former electronic mails will be hereinafter referred to as instant mails, and the latter will be referred to as non-instant mails. In this manner, electronic mails can be classified into two groups. Like the normal mail delivery services, there are instant mails that are equivalent to express mail, and non-instant mails that are equivalent to ordinary mail. In general, express mail is delivered quicker than ordinary mail, and therefore the price rates for express mail are higher than the price rates for ordinary mail. Ordinary mail is delivered at lower costs than express mail, because it requires more days to be delivered. However, even though there are instant mails (equivalent to express mail) and non-instant mails (equivalent to ordinary mail) in the electronic mail delivery services, users have to pay the same price for either of the services. This fact makes the users feel unfairness about the price system.